The Abilene reflector. [volume] (Abilene, Kan.) 1883-1888, 1887-09-15
GATHERING THE GOLD.
Methods Adopted for Getting the Metal
Out of the Free Milling Ore.


! Out of the Free Milling Ore.
! At Breckenridge, Col. the other day.
I saw the Jumbo st;rmp-mill. and there
got fair insight into the method of
getting the gold out of what is called
free milling. ore. The stuff that comes
from the mine is first pat through a
rrusher, which breaks It mp fine, and
: the product is then run through rollers
which pulverizes it, though, perhaps.
coarsely. From the rollers it falls to
the lower floor, upon which the NOR
| tars are located. At the Jumbo mill
the dirt is fell to the stamps b. hand;
/ in other mills it falls through chutes
which work automatically, and never
feed more than is necessary at a
I time. The stamps are arranged in
batteries OF five stamps each. They
work up and down in oak easements,
and their motions are regulated by
cams on shaft gearcd to the motive
machinery. The stamps weigh from
$50 to 900 pounds, according to TIE
character of the ore treated. Water
/ flows into the mOrtars and ont of them
down tables to the waste fumes which
carry the refuse away. Stamps in this
country run as low as thirty drops n
minute, and seldom over Sky; in
California they drop seventy To 100
times 4 minute. The two kinds of mills
are distinguished by the rapidity or
! slowness of their drops. and those used
here are all built by Peter Mcfarland,
and are called Giipin County mills,
from McFariand's home place, which
is in Gilpin County, while the others
are known as California mills. They
cost from 500 for Il five-stImp pros
pccting mill to $4,000 for 100-stamp
mill. The dirt being fed into the mortars
is pounded and pounded By the stamps;
the silica, porphyry and other refuse
is carried off by TIE water, but the gold
is caught by two copper plates coated
with quicksilver that line the sides of
the mortar; any of the precious metal
that escapes from the mortar may be
caught on the 4xS feet copper plates
that are quicksilver coated and lie on
the table over which the refuse is car
ried. Some of the gold gets away, OF
course, but the Jumbo saves as much
as 80 per cent. of its gold. and McFar-
land is now building mills which he
claims will save 50 per cent. of the as
sayed value of ore.
Concentrators are used where the ore
is too low grade to pay for smelling in
its crude state. BY concentrating so
or S12 ore may be handled so that the
mill product, which will represent six
or seven tons in ore, may be worth $40
to $50 per ton. The scheme IS very
simple. The crushed and rolled ore is
fed through chutes to revolving screens
ranging in size from three-fOurths inch
openings to one-eighth. Each of these
screens has trough and chute which
feeds a Jig box. The jig boxes work on
an eccentric and keep up spasm-like
motion. There is screen in each about
six inches from the top, and this screen
is covered with lead or other heavy
ore material, which prevents tn.
silica. porphyry and other light stuff
from going through. The motion
shakes the metal to the bottom of the
boxes, where it remains until valves in
the bottom are opened and the concen-
trates are removed. This machine, like
all the others called by different names,
and known as triumps, frue vanuers,
bubbles, bump plates, etc, is an appli-
cation of the well-known law of specific
gravity; the heaviest material falls to
the bottom in all ttlesc machines, and
the light stuff goes dancing away on
the water. The bump plate. which is
claimed to be a new invention by Peter
Mcfarland, is large steel plate set at
an incline of few degrees; the ore is
fed to the lower part of the place from
a water trough. and as the high end
bumps it carries forward and up over
the top of the plate the heavy concen-
trates. Cor. st. Louis Globe Democrat.